ARC: SMP support
ARC common code to enable a SMP system + ISS provided SMP extensions.
ARC700 natively lacks SMP support, hence some of the core features are
are only enabled if SoCs have the necessary h/w pixie-dust. This
includes:
-Inter Processor Interrupts (IPI)
-Cache coherency
-load-locked/store-conditional
...
The low level exception handling would be completely broken in SMP
because we don't have hardware assisted stack switching. Thus a fair bit
of this code is repurposing the MMU_SCRATCH reg for event handler
prologues to keep them re-entrant.
Many thanks to Rajeshwar Ranga for his initial "major" contributions to
SMP Port (back in 2008), and to Noam Camus and Gilad Ben-Yossef for help
with resurrecting that in 3.2 kernel (2012).
Note that this platform code is again singleton design pattern - so
multiple SMP platforms won't build at the moment - this deficiency is
addressed in subsequent patches within this series.
Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Rajeshwar Ranga <rajeshwar.ranga@gmail.com>
Cc: Noam Camus <noamc@ezchip.com>
Cc: Gilad Ben-Yossef <gilad@benyossef.com>
diff --git a/arch/arc/Kconfig b/arch/arc/Kconfig
index 68350aa..52f5c07 100644
--- a/arch/arc/Kconfig
+++ b/arch/arc/Kconfig
@@ -116,9 +116,42 @@
help
Build kernel for Big Endian Mode of ARC CPU
+config SMP
+ bool "Symmetric Multi-Processing (Incomplete)"
+ default n
+ select USE_GENERIC_SMP_HELPERS
+ help
+ This enables support for systems with more than one CPU. If you have
+ a system with only one CPU, like most personal computers, say N. If
+ you have a system with more than one CPU, say Y.
+
+if SMP
+
+config ARC_HAS_COH_CACHES
+ def_bool n
+
+config ARC_HAS_COH_LLSC
+ def_bool n
+
+config ARC_HAS_COH_RTSC
+ def_bool n
+
+config ARC_HAS_REENTRANT_IRQ_LV2
+ def_bool n
+
+endif
+
+config NR_CPUS
+ int "Maximum number of CPUs (2-32)"
+ range 2 32
+ depends on SMP
+ default "2"
+
menuconfig ARC_CACHE
bool "Enable Cache Support"
default y
+ # if SMP, cache enabled ONLY if ARC implementation has cache coherency
+ depends on !SMP || ARC_HAS_COH_CACHES
if ARC_CACHE
@@ -213,6 +246,8 @@
default n
# Timer HAS to be high priority, for any other high priority config
select ARC_IRQ3_LV2
+ # if SMP, LV2 enabled ONLY if ARC implementation has LV2 re-entrancy
+ depends on !SMP || ARC_HAS_REENTRANT_IRQ_LV2
if ARC_COMPACT_IRQ_LEVELS
@@ -261,6 +296,8 @@
bool "Insn: RTSC (64-bit r/o cycle counter)"
default y
depends on ARC_CPU_REL_4_10
+ # if SMP, enable RTSC only if counter is coherent across cores
+ depends on !SMP || ARC_HAS_COH_RTSC
endmenu # "ARC CPU Configuration"
@@ -309,7 +346,7 @@
config ARC_DBG_TLB_PARANOIA
bool "Paranoia Checks in Low Level TLB Handlers"
- depends on ARC_DBG
+ depends on ARC_DBG && !SMP
default n
config ARC_DBG_TLB_MISS_COUNT
